SLVSB53A May   2012  – December 2014

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Typical Application Schematic
  5. 5 Revision History
  6. 6 Device Options
  7. 7 Pin Configuration and Functions
  8. 8 Specifications
    1. 8.1 Absolute Maximum Ratings
    2. 8.2 ESD Ratings
    3. 8.3 Recommended Operating Conditions
    4. 8.4 Thermal Information
    5. 8.5 Electrical Characteristics
    6. 8.6 Typical Characteristics
  9. 9 Parameter Measurement Information
  10. 10Detailed Description
    1. 10.1 Overview
    2. 10.2 Functional Block Diagram
    3. 10.3 Feature Description
      1. 10.3.1 Controller Circuit
        1. 10.3.1.1 Startup
        2. 10.3.1.2 Operation at Output Overload
        3. 10.3.1.3 Undervoltage Lockout
        4. 10.3.1.4 Overvoltage Protection
        5. 10.3.1.5 Overtemperature Protection
    4. 10.4 Device Functional Modes
      1. 10.4.1 Device Enable and Shutdown Mode
  11. 11Application and Implementation
    1. 11.1 Application Information
    2. 11.2 Typical Application
      1. 11.2.1 Design Requirements
      2. 11.2.2 Detailed Design Procedure
        1. 11.2.2.1 Adjustable Output Voltage Version
        2. 11.2.2.2 Inductor Selection
        3. 11.2.2.3 Capacitor Selection
          1. 11.2.2.3.1 Input Capacitor
          2. 11.2.2.3.2 Output Capacitor
      3. 11.2.3 Application Curves
  12. 12Power Supply Recommendations
  13. 13Layout
    1. 13.1 Layout Guidelines
    2. 13.2 Layout Example
    3. 13.3 Thermal Considerations
  14. 14Device and Documentation Support
    1. 14.1 Device Support
      1. 14.1.1 Third-Party Products Disclaimer
    2. 14.2 Documentation Support
      1. 14.2.1 Related Documentation
    3. 14.3 Trademarks
    4. 14.4 Electrostatic Discharge Caution
    5. 14.5 Glossary
  15. 15Mechanical, Packaging, and Orderable Information

11 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

11.1 Application Information

The TLV61220 is intended for systems powered by a single cell battery to up to three Alkaline, NiCd or NiMH cells with a typical terminal voltage between 0.7 V and 5.5 V. It can also be used in systems powered by one-cell Li-Ion or Li-Polymer batteries with a typical voltage between 2.5 V and 4.2 V. Additionally, any other voltage source with a typical output voltage between 0.7 V and 5.5 V can be used with the TLV61220.

11.2 Typical Application

TLV61220 pmi_schem776rev3[1].gifFigure 14. Typical Application Circuit for Adjustable Output Voltage Option

11.2.1 Design Requirements

In this example, TLV61220 is used to design a 3.3-V power supply with up to 50-mA output current capability. The TLV61220 can be powered by a single-cell battery to up to three Alkaline, NiCd or NiMH cells with a typical terminal voltage between 0.7 V and 5.5 V. It can also be used in systems powered by one-cell Li-Ion or Li-Polymer batteries with a typical voltage between 2.5 V and 4.2 V. In this example, the input voltage range is from 2 V to 3 V for one-cell coin cell battery input design.

Table 2. TLV61220 3.3 V Output Design Requirements

PARAMETERS VALUES
Input Voltage 2 V to 3 V
Output Voltage 3.3 V
Output Current 50 mA

11.2.2 Detailed Design Procedure

Table 3. List of Components

COMPONENT REFERENCE PART NUMBER MANUFACTURER VALUE
C1 GRM188R60J106ME84D Murata 10 μF, 6.3V. X5R Ceramic
C2 GRM188R60J106ME84D Murata 10 μF, 6.3V. X5R Ceramic
L1 1269AS-H-4ZR7N Toko 4.7 μH
R1, R2 R1= 1MΩ, R2= Values depending on the programmed output voltage

11.2.2.1 Adjustable Output Voltage Version

An external resistor divider is used to adjust the output voltage. The resistor divider needs to be connected between VOUT, FB and GND as shown in Figure 14. When the output voltage is regulated properly, the typical voltage value at the FB pin is 500 mV. The maximum recommended value for the output voltage is 5.5 V. The current through the resistive divider should be about 100 times greater than the current into the FB pin. The typical current into the FB pin is 0.01 μA, and the voltage across the resistor between FB and GND, R2, is typically 500 mV. Based on those two values, the recommended value for R2 should be lower than 500 kΩ, in order to set the divider current to 1 μA or higher. The value of the resistor connected between VOUT and FB, R1, depending on the needed output voltage (VOUT), can be calculated using Equation 1:

Equation 1. TLV61220 eq_R1R2_Vo_lvs776.gif

As an example, if an output voltage of 3.3 V is needed, a 1-MΩ resistor is calculated for R1 when for R2 a 180-kΩ has been selected.

11.2.2.2 Inductor Selection

To make sure that the TLV61220 can operate, a suitable inductor must be connected between pin VBAT and pin SW. Inductor values of 4.7 μH show good performance over the whole input and output voltage range .

Choosing other inductance values affects the switching frequency f proportional to 1/L as shown in Equation 2.

Equation 2. TLV61220 q_6_lvs776.gif

Choosing inductor values higher than 4.7 μH can improve efficiency due to reduced switching frequency and, therefore, with reduced switching losses. Using inductor values below 2.2 μH is not recommended.

Having selected an inductance value, the peak current for the inductor in steady state operation can be calculated. Equation 3 gives the peak current estimate.

Equation 3. TLV61220 q_3_lvs776.gif

For selecting the inductor this would be the suitable value for the current rating. It also needs to be taken into account that load transients and error conditions may cause higher inductor currents.

Equation 4 helps to estimate whether the device will work in continuous or discontinuous operation depending on the operating points. As long as the inequation is true, continuous operation is typically established. If the inequation becomes false, discontinous operation is typically established.

Equation 4. TLV61220 q_1_lvs776.gif

The following inductor series from different suppliers have been used with TLV61220 converters:

Table 4. List of Inductors

VENDOR INDUCTOR SERIES
Toko DFE252010C
Coilcraft EPL3015
EPL2010
Murata LQH3NP
Taiyo Yuden NR3015
Wurth Elektronik WE-TPC Typ S

11.2.2.3 Capacitor Selection

11.2.2.3.1 Input Capacitor

At least a 10-μF input capacitor is recommended to improve transient behavior of the regulator and EMI behavior of the total power supply circuit. A ceramic capacitor placed as close as possible to the VBAT and GND pins of the IC is recommended.

11.2.2.3.2 Output Capacitor

For the output capacitor C2, it is recommended to use small ceramic capacitors placed as close as possible to the VOUT and GND pins of the IC. If, for any reason, the application requires the use of large capacitors which can not be placed close to the IC, the use of a small ceramic capacitor with an capacitance value of around 2.2μF in parallel to the large one is recommended. This small capacitor should be placed as close as possible to the VOUT and GND pins of the IC.

A minimum capacitance value of 4.7 μF should be used, 10 μF are recommended. If the inductor value exceeds 4.7 μH, the value of the output capacitance value needs to be half the inductance value or higher for stability reasons, see Equation 5.

Equation 5. TLV61220 q_5_lvs776.gif

The TLV61220 is not sensitive to the ESR in terms of stability. Using low ESR capacitors, such as ceramic capacitors, is recommended anyway to minimize output voltage ripple. If heavy load changes are expected, the output capacitor value should be increased to avoid output voltage drops during fast load transients.

11.2.3 Application Curves

FIGURE
Load transient, VI = 1.2 V, VO = 3.3 V, IO = 5mA to 20 mA Figure 15
Line transient, VI = 1.8 V to 2.4V, VO = 3.3 V, IO = 30 mA Figure 16
Startup after Enable, VI = 1.2 V, VO = 3.3 V, RLOAD = 50 Ω Figure 17

spacing

TLV61220 Figure10rev1.gifFigure 15. Load Transient Response
TLV61220 Figure11rev1.gifFigure 17. Start Up After Enable
TLV61220 Figure9rev1.gifFigure 16. Line Transient Response